Isn't the more common (and easier to say) "representation" good enough in its place?
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FoscoAug 2 '11 at 18:00

It crops up in a bio science text I'm proofreading today. Apparently it's quite common usage in eco texts, like this one about fish: "...2 specimens were returned to the stream and not considered in this study due to their low representativity."
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Leni NawocamAug 21 '14 at 9:10

5 Answers
5

It is a morphologically valid construction. For example, see the same pattern in relative/relativity (where the latter is a rather recent derivative of the former)

It is commonly used in the field of statistics (see Google Scholar searches for “representativity + statistics” or related terms).

Examples of its use in academic writing include the following (found using the Corpus of Contemporary American English), both in and outside of the field of statistics:

A school based sample of 5,500 Norwegian 16 to 19 year olds (92% response rate) with good population representativity was analyzed. Same-sex experiences included “necking” / “making out”, petting, intercourse, and oral sex. Compared to heterosexual young people, young people reporting same-sex sexual experiences only were more socially integrated into their peer group and consumed more alcohol.

(K. Hegna, Journal of Drug Issues, 2007, vol. 37, p. 229)

The conventions of representation are bankrupt, for their legitimacy rested on representativity as much as on resemblance or mimesis. Abstract art used to register the bankruptcy, but, abstract art has long been assimilated and has lost its critical edge.

Representativity is valid morphologically and semantically. As for the "representativity" or representativeness debate, think of how wrong some of these word would sound ie "flexibileness" (sic) or intelligiblness (sic) or illegibileness (sic). No, adding -ness as an ending is not a panacea, and yes, the English language is more creative and adaptable than some readers might want to think.

I have come across this word for the first time today (I am 75) and have quite happily managed to live without it so far. It sounds to me like something made up by an American Newsreader, morphologically correct or not, and certainly a word we can do without quite happily.

I agree with Mechanical Snail — if the word is required, use 'representativeness', but there must be a better alternative. Now for Roget's.

'representativity' appeared as a linguistic calque committed by foreign users of English unaware that the English derivative is constructed with the Germanic suffix '-ness' rather than the Latin suffix '-atis' (very productive in English, too: civility, productivity, mayoralty, etc.), as it happens in other European languages: Fr - representativite; It - representativita; Ro - reprezentativitate, etc.

And why shouldn't we add -ity to nouns of French origin? The words sensibility and activity came directly from the French words sensibilité and activité. According to etymonline, productivity didn't originate with the French word productivité, but came from productive + -ity. But why was that wrong? I would say it's quite likely that this suffix was added by a native speaker of English who knew French, and not by a foreigner.
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Peter Shor Nov 28 '13 at 5:38